'''
def changenum(num):#函数参数，副本机制，新建一个变量
    print("changenum",id(num))
    num=100
    print("changenum",id(num))

num=10
print("main", id(num))
changenum(num)
print(num)
print("main", id(num))
'''

def changenum(num):#函数参数，副本机制，新建一个变量
    print("changenum",id(num))
    num="21321321"
    print("changenum",id(num))

num="12321"
print("main", id(num))
changenum(num)
print(num)
print("main", id(num))
